Has to be a loose vacuum hose or vacuum cannister.
I'm not familar with late model Mustangs, so someone else chime in here.
If there is a vacuum canister in the engine compartment it is very easy to knock loose a hose resulting in a dash control problem. The cannister should be about the size of a grapefruit, black, with two hoses going to it.
If you recently installed a stereo or did some work under the dash possibly a hose was knocked loose.
The vacuum 'motors' that actuate the various vents and the dash control itself are very reliable and do not fail often. |